click the mouse and drag in a direction to rotate the scene in real time

In the beta version you can choose your rotating frame rate by choosing an object from the dropdown list, and it will set the rotating frame period to the orbital period of the selected object.

Then, since this is only a good estimate, you can use the calibrate button on the menu option to home-in on the precise period.

To use this:

Open the "Rotating Frame Adjustment" interface by "View> Rotating Frame Adjustment" Press the Calibrate button once. The mouse icon will change to "crosshairs" when you drag it over the simulation. Click on the object you want to hold stationary.

Wait... the longer, the better. When the object you want to hold stationary drifts an appreciable amount, click it again. Your 2 clicks will tell Gravity Simulator how much the frame is drifting, and it will adjust accordingly. After clicking the object for the 2nd time, your mouse icon will change back to normal.